Impedance variation amplifier



M r-ch 23, 1937. w. H. HOWE 2,0?4396 IMPEDANCE -VARIAT ION AMPLIFI ER Filed March 11, 1935 4 Sheets-Sheet l 11 2 Z2. M I i i v ,Tl" l I l f gal v I f March 23, 1937. w, H HOWE 2,074,396

IMPEDANCE VARIATION AMPLIFIER Filed March 11, 1933 4 Sheets-Sheet 2 F I I I 1 I l i l I March 23, 1937.- w. H. HOWE I 2,074,396

I IMPEDANCE VARIATION AMPLIFIER Filed March 11, 1933 4 Sheets-Sheet 3 March 23, 1937. w. H. HOWE 2,074,396

IMPEDANCE VARIATION AMPLIFIER Filed March 11 1953 4 Sheets-Sheet 4 0%12 a'rm'l 002w UNiTED STATES PATENT OFFICE meme assignments, to The Cincinnati Milling- Machine 00., Cincinnati, Ohio, a corporationof Ohio Application March -11, loss, Serial-No. scam This invention has-for an object to produce an amplifying effect on a'controlled circuit similar to that which may be obtained by, certain circuits employing vacuum tubes or other voltage or 5 poweramplifying devices, but without the use of smn tubes or devices. This. is accomplished to this invention .by variation of impedance suitably connected to a source oi alternating power. to control voltage to or through a circuit, the-variations of this impedance being controlled by very much smaller variations in a controlling impedance. This may be accomplished entirely by suitable combinations of inductance, capacity and resistance designed" for iii any desired single trequency. as will later more fully appear. z

A simple tcircuit with asingle inductance and a single capacity, both of approximately impedance-at the frequency .atrwhich 2o they'are operated, behavesas an'impedance variation ampliiler. a small change of inductance or capacity resulting in a large. change of the eifective imp edance of the system. However, therelic of change of-total impedance to change of inductance or .capacity cannot be maintained 35 ly i1 it. contains very rapidly the enectivenessofthesimple resonancecircuit' asanampliilerofimfiedancevariation. I

minductanceandcapacityinseries theimpedanceofthe total varlefwithra variation of and reaches-"a minimumiwhen the 1m? pedance is equal to the impedance of the inductance and capacity in the impedance *0! the total varies, a when the impedance o! the capacity isequalto the impedance of the inductance. 1f the resistances 'hf the inductance and caMWa-re smailethat is. if.the factor is low, then the impedance at'series resonance is much lea than the impedance of either inductt0 ance or capacity, while the impedance at parallel resonance is much than that oi either inductanceorcapacity.- I

arranging 'a circuitnet work that a relatively small change of inductance or capacity will 55' produce a change 'i'rom a state of eilective parallel (c1. sz-u') resonance to effective series resonance, a condition' is reached where the small change of re-' actance; either of capacity or' inductance, produces a' large change in impedance of the net work. I It is upon this principle thatthe circuit of 6 this, invention operates. Such an arrangement is extremely flexible in operation. It is possible to so arrange the proportions that s, very wide range of ratios between controlling and controlled impedance may be effected and this ratio .may 10 be. adjusted at will. Within fairly wide limits the ratio of change of voltage or current to change of .impedance.may be made a constant,

or it maybe made to vary with change of controlling impedance. By connecting an out-put l5 circuit even of relatively large power capacity in parallel th the controlled impedance, a relatively l ge change in the voltage, current, and power. out-put of this circuit may be produced by a small variation in the controlling reactancc gorange of controlled network impedance: second, 30

that this ratio can be easily varied or may be caused to vary wi changes in controlled network impedance: third, at a relatively large amount of power may be drawn from this circuit and supplied to any desired. out-Rut circuit,-and, fourth,. '35

that the circuit is very readily adaptable to use in common" with a low potential coupling line whereby. the controlling inductance or capacity may be separated a considerable distance from the point tc which the .out-put circuit' is con- 40 nected to the controlled netwotk impedance, the coupling itself being relatively insensitive tochanges'of its impedance or capacity to ground,

a feature frequently of great importance when dealing withhigh irequenciesn circuit is 45 relatively insensitive to'resistance variations and the eifect of resistance variations canbe stilli'urthin-"minimized at desired points by a suitable v choice of the fixedreactances. Thus the poikntial variations ot the net work are governed substantially entirely by variation'sflof reactance and the current through the network varies between -a value approaching that of the supply potential divided by in-put impedance and the value approaching zero, depending on the variations of quency fed to the series-paralleicircuit through the impedance 2, it is possible to omit the impedance 2 provided the source of alternating curpendent of the impedance of the circuit through which it fiows. 10 A large number of amplifications of the simple circuits of Figuresl and 2 is possible, but for the.

sake of simplicity some of these based on the elemental circuit of Figure '1 will be further considered', it being understood, however, that these 15 may be rearranged as in Figure 2 if desired so long as the proper relations in values are rved. Thus the various units instead of being n the forms of simple inductance or capacityor resistance units may be more comprehensive. In Fig- 20 ure 4, for example,'the impedance 2' is shown in the form of a loose coupled transformer and in Figure the reaetance 2' is shown as an auto-. transformer, though a full insulating transformer might be substituted, and the connection to the unit 0 may be taken of! at a diiferent point from the connections to the impedance 2. It is also possible to take oil the out-put circultacross to operate at the voltage E2, or it maybe in series with the reactance 2, and operate on current'variations in the amplifier circuit. Further, any of the impedances maybe circuits, each having as a whole suitable values of inductance, capacity or resistance and they may beconnected in' through suitable leads. For example, in Figure 3, the unit or head comprising thesomewhat loosely coupled transformer II and the variable condenser ll so related to each other that the whole is capacitive, may take the place of the condenser 5 in Figure 1. In order that it may be '40 capacitive, the'capa'city'of the controlling conhave it small, easily movable, and at some dis-v tance from the remainder of the circuit. So. as 50 shown, it is connected by a coupling circuit including the leads I2. The condenser ll may be a variable measuring condenser as shown, for example, in either of the Allen'Patents No. 1,708,073 and -No. 1,708,074, both granted April 9, 1929. When the ratio of the transformer II is low and it is sufiiciently loose coupled, though it cannot be a very loosely .coupledbecause of the loss of-sen- .fsitlvity of the circuit, variations of internal capacity and of capacity to ground of leads l2 'do 60 not act appreciably on the control head, nor on other parts of the circuit. This feed line is then so nearly aperiodic that the leadsv l2 may com- ,prlse an ordinary lamp cord several feet in length and may be moved around with no appreciable 65 effect. while the head circuit is subjected to measuring changes of the condenser ll of the order of Illfarads. In Figures 6, 7 and 8 various types of industrial circuits employing the general arrangements of in amplifying circuit of Figure 1 are illustrated by way of example, though it should be understood that these arrangements are applicable to many others. The source of power may be a vacuum tube oscillator circuit. 75 Figure 6 is a diagram of a condenser rnicrov 3 phone set-up. The source 'of power is any suitable oscillator connected to the lines is and it.- It is not necessary that its frequency be particularly constant. -Thc microphone is indicated at I! and corresponds in so faras its function in the amplifying circuit is concerned to the control head comprising the parts Ill and it of Figure 3. The controlling variable condenser II is formed by a fixed plate set close to the diaphragm of'a microphone. Sound waves striking the diaphragm cause it to vibrate and vary the capacity of this condenser. Since the diaphragm is entirely unloaded, the capacity variation corresponds very closely to sound pressure variation in a properly designed instrument. While this microphone unit contains an inductance I! as pacitive as in Figures 1 and 4: The out-put circult is taken off in parallel with the reactance 2 and as shown may be a vacuum tube rectifying circ'uit indicated generally at 20 from which it emerges as audio frequency electrical waves corresponding exactly to the sound waves which produce them. The combination of effective amplification of both impedance and controlled power, makes possible the elimination of two,

stages of vacuum tube amplification, materially reduces oscillator frequency stabilization requirements, reduces the size and materially simplifies the construction of the microphone proper and makes the whole' apparatus much more stable and simple to operate than were this amplifica- I tion produced by vacuum tube stages. Instead of rectifying the power out-put-from this impedance amplifier circuit, it could be directly amplified and fed to an antenna system for broad-- casting if desired. 3 v

Figure 7 shows a complete position responsive circuit patterned after that of Figure 3 but showing the actual oscillator and out-put circuits. This complete circuit may be used to indicate minute variations of physical dimensions, causing-these variations of dimensions to vary capacbodying' the self-compensating features of the circuit shown in the Field Patent No- 1,813,488 granted July 7, 1031, operating directly from a 110 volt -cycle lighting circuit. This circuit operates with the compound secondary circuit herein shown, as well as with the single resonant secondaryshown in the Field patent. The output circuit of Figure 7 consists of a high resistance high frequency voltmeter comprising a rectifying tube 22, a high resistance 24. radio and audio frequency chokes 25 and 26, respectively, and a low current ammeter 21. By using a meter with a suppressed zero a uniform scale reading directly in variation of dimension over" the entire scale.

contour of a pattern as followed by a tracer which is made to traverse the pattern.

Figures 9 and 10 show sumcient of the machine construction to show the relations of the tool mousse 5 between the tworesonant-points which, however,

are maintained at substantially the same output voltage.

In Figure 15 the curves beyond the resonance ii points have been varied without change between them. InPlgure 16 thecurve between'the resomce points, departs substantially irom'straight l'lgnre 1"! is somewhat similar to Figure 15,-ex-

10 cent that the curve beyond the resonance points is still further modified. r In Figure 18 the major portion of the curve between the resonance points is unchanged but the maximum and minimum out-put voltages are 16 less widely separated.

From the foregoing description 01' this invention and certain circuits in which the invention has been shown as embodied, it will be evident to those skilled in the art that various other 20 changes and modifications might'be made without departing from the spirit orscope of this invention as defined by the appended claims.

I'claim:

1. In combination, three reactances at least 25 one oi ,which is inductive, at least one of whichjs capacitive, and at least-one of which is variable,

said reactances being in series parallel arrangement ina circuit and of relative values such that small variations in said one variable reactance 30 cause impedance of the circuit as a-wholeto' pass between conditions of parallel and series resonancerthereby producing a large variation in impedance of the circuit as a whole as the result 01 such small variations in said variable reactance.

2. In combinatlonsan alternating current "cir- .cuit comprising an impedance, three reactances in series with said impedance, two of said'reactances being arranged in series with each other and one or said two in parallel with the third, at least one of said two reac'tances being variable, said reactances being at such relative values that variation of said one variable reactance causes variations in said circuit between series and parallel resonance, and an output circuit con nected to said first mentioned circuit.

3. In combination, an alternating current circuit comprisingan impedance, a reactance in series with said impedance, a pair of reactances in 60 said circuit one of which is capacitive and the other oi which is inductive .and at least one oi which is variable, said reactances being in seriesparallel arrangement and of relative values to cause variation of said-one variable 'reactance to 55 cause variations between series and parallel resonance in said circuit, and an out-put circuit cimnected to said first mentioned circuit.

4. In combination, a series-parallel circuit con sisting 01' three reactive impedances, at least one so oi which is capacitive and at least one oi which is inductive and one or which is variable, the values and arrangements oi said impedances' be- 'such that small variations in said one'varie impedance produce much larger changes in 6,5 theimpedances of said circuit as a whole, a

source of substantially constant frequency and current value alternating current power connected to said'circuit, and snout-put circuit deriving power from said series parallel circuit. 70 5. In combination, a series-parallel circuit consisting of three reactiveimpedances, at least one of which is capacitive and at least one of which is inductive and one of which is variable, the values and arrangements of said impedances 16 beingsuchthatsmallvariationsinsaidonevariableimpedanceproducesmuchlargercbangesin the impedances oi said-circuit as a whole, a source of substantially constant frequency .and potential alternating current po'wer, means in-- "cludinga coupling impedance for connecting said source'to said circuit, and an out-put circuit derivlng power from said series-parallel. circuit.

6. In combination, an alternating current circuit comprising an impedance, a series-parallel circuit comprising a reactance in series with said impedance, an inductance and a capacity, at least one being variable, inseries with each other and both together in parallel with saidreactan the relative values and characteristics of said reactances and the relative values oi saidcapacity i5 and inductance being such that variation of said one variable causes change between series and parallel resonance between said reactance, capacity and inductance, and an output circuit .de--

- riving power from said series-parallel circuit.

7. In combination, an alternating current circuit comprising an impedance, a series parallel circuit comprising a. reactance in series with said impedance, aninductance and a capacity at'least one being variable, in parallel with each other and both together in series with said reactance, the relative values and characteristics 0! said reactances and the relative values of said capacity and inductance being such that variation or said one variable causes change between series and parallel resonance between said reactanceg capacity and inductance, and an out-put circuit deriving power from said series-parallel circuit.

8. In combination, an alternating current circuit comprising an impedance, a series-parallel circuit comprising a capacity in series with said impedance, an inductance and a variablecapacity. in series with each other and both in parallel with said first mentioned capacity, said capacities. and inductance being of'such relative values that variations of said variable capacity causes change in said series-parallel circuit between'series resonance between said variable capacity and inductance and parallel resonance between said variable capacity and inductance together andsaid first mentioned capacity, and an out-put circuit de-.

'riving power from said series-parallel circuit.

'9. In combination, a series-parallel'circuit consisting of three reactive impedances, at least one 01- which is capacitive, at least one of which is so inductive and at least one of which is variable, said one-variable impedance being responsive in its variations to a controlling variable to which an amplified response is desired, and having a low voltage connection with the other oi said impedances, a source of substantially constant irequency and "potential alternating current power, means including a coupling impedance connecting said source to said circuit, and an output circuit deriving power from said series-par- 0 allel circuit. v

10. In combination, a series-parallel circuit consisting oi three reactive impedances, at least one 01 which is capacitive, at least one of which is inductive, and at least one of which is vari- 5 able, a measuring devic'eof which said one variable impedance forms a part and the value at which is responsive to that 01' the variable being measured, a source of substantially constant frequency and potential alternating current power, 7 means including a coupling impedance connecting said source to said circuit, and an'indicator r nsive to electrical conditions of said circuit.

11. In combination in a machine for controlling the feed of a cutting tool to reproduce on a 7 $0 relativev movement pat-. tern suthcejand a said and tin ' -fl.'nlomethodoflmplifying variationsoia m'whidim l m' flonsnt-idomrenctancetovarycircuitreacserieswithanimpedanceoi oi! amplified sewhich is ca l'enctanesinssidneirworkoueoi indnctiveand responsivetoslnallchnngq nt dectrical renctance'comprisin'ga tooland madirectcurrent stantially constant potential and irequencyuon in-put impethnce, and. a network comprising threereactiveimpedanm-atleastoneoiwhich n capacitive antLat least one oi which is inductive and one or which is variable, the values and cuts 01 said impedances being such that small variations in said one variable impedance .produce much larger changes in the impedsnce oi the network as awhole, andan output circuit deriving power from said network. "J 16. In combination, three at least one .oi which is inductive, at least one 0! which is capacitive, and at least one 01! which is vari ranxement in'a circuit and 0! relative values such that small variations'insaidone varhble thereby tloninimpedsnceoi'thecircuitasawholeasa resultotmnchsmallervariationsinsaidvarh ablereactm'ice.

oneo! which is network being so able, said reaetancels being in series parallel ararranaedthat-asmallchsnzeoireactanceofsaidonevariahlexecctancewill ,causethe otthenetwork asawhols tovarybetweenvahieslnrgeandsmallinnmportion or the in-put impedance, thereby causing thepotentlalacmssthenetwork'tovarybetweensvamethepotentisiotsaid supplysourceand'avalneapwoachinglermand variation.

1am electricaisystemresponsivetossnall changes of electrical reluctance. a som'ceotalternaflngcurrentensrgyoisuhstan- @tially constant potentialand a'nstwoi-Lasulltanttfllyconstnnt through 'whichenergytrom'saidswrceisslmpliedtoaaid netwm'hiitleastthmeinsiiidmat workatleastoneofwhichisinductiveandat leastoneotwhichiscapacitiveandstleistonc actance of said one variable reactance will cause the impedance of the net work as a whole to vary between values large and small in proportion to the in-put impedance, thereby causing the potential across the network to vary between a value approaching the potential of said supply source'and a value approaching zero, said variations of impedance and potential being governed substantially entirely by variations of reactance and being substantially entirely independent of variations of resistance of said variable reactance.

20.-An electrical system responsive to small changes of electrical reactance, comprising a source of alternating current energy of substantially constant potential and frequency, a network, a substantially constant impedance through which energy from said source is supplied to said network, at least three reactances in said network at least one of which is inductive and at least 20 one of which is capacitive and at least one of which is variable, the network being so arranged that a small proportionate change of reactance of said one variable reactance will cause the vimpedance of the network as a. whole to vary 25 between values large and small inproportion to the input impedance, thereby causing the current through said network to vary between a value approaching that of the supply potential divided by the in-put impedance and a value approaching zero, said variations of impedance and cur .rent being governed substantially entirely by variations of reactance and substantially entirely independent of variations of resistance of said variable reactance.

21. An electrical circuit supplied-with alternating current power of substantially constant frequency comprising at least three impedances at least one of which is variable, said impedances having such relative values that variation in said variable impedance causes the impedance of the circuit as a whole to vary between the conditions of parallel and series resonance, thereby producing a variation in the impedance of the circuit as a whole.

22. An electrical circuit supplied with frequency comprising at least three impedances, at least one of which has an effective inductive reactance, at least one of which has effective capacitive reactance, at least one of which is variable, said impedances connected in series-parallel and having such relative values that variation in saidone variable impedance causes the impedance of the circuit as a whole to vary between the conditions of parallel and series resonance, thereby producing a variation in the impedance of the circuit as a whole.

' W H. HOWE.

CERTIFICATE or CORRECTION.

Patent no. 2,074,396.

March 25, 1937.

WILFRED H. HOWE.

It is hereby certified that error appears in the pr 01 the above numbered patent requiring correction as follows: second column, line 46, strike out the word 'of" after "series"; and that the said Letters Patent should be read i Pag the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of April, "A. D. 1937.

(Seal) Leslie- Frazer alter-' nating current power of substantially constant.

inted specification with this correction therein that Acting Commissioner of Patents.

actance of said one variable reactance will cause the impedance of the net work as a whole to vary between values large and small in proportion to the in-put impedance, thereby causing the potential across the network to vary between a value approaching the potential of said supply source'and a value approaching zero, said variations of impedance and potential being governed substantially entirely by variations of reactance and being substantially entirely independent of variations of resistance of said variable reactance.

20.-An electrical system responsive to small changes of electrical reactance, comprising a source of alternating current energy of substantially constant potential and frequency, a network, a substantially constant impedance through which energy from said source is supplied to said network, at least three reactances in said network at least one of which is inductive and at least 20 one of which is capacitive and at least one of which is variable, the network being so arranged that a small proportionate change of reactance of said one variable reactance will cause the vimpedance of the network as a. whole to vary 25 between values large and small inproportion to the input impedance, thereby causing the current through said network to vary between a value approaching that of the supply potential divided by the in-put impedance and a value approaching zero, said variations of impedance and cur .rent being governed substantially entirely by variations of reactance and substantially entirely independent of variations of resistance of said variable reactance.

21. An electrical circuit supplied-with alternating current power of substantially constant frequency comprising at least three impedances at least one of which is variable, said impedances having such relative values that variation in said variable impedance causes the impedance of the circuit as a whole to vary between the conditions of parallel and series resonance, thereby producing a variation in the impedance of the circuit as a whole.

22. An electrical circuit supplied with frequency comprising at least three impedances, at least one of which has an effective inductive reactance, at least one of which has effective capacitive reactance, at least one of which is variable, said impedances connected in series-parallel and having such relative values that variation in saidone variable impedance causes the impedance of the circuit as a whole to vary between the conditions of parallel and series resonance, thereby producing a variation in the impedance of the circuit as a whole.

' W H. HOWE.

CERTIFICATE or CORRECTION.

Patent no. 2,074,396.

March 25, 1937.

WILFRED H. HOWE.

It is hereby certified that error appears in the pr 01 the above numbered patent requiring correction as follows: second column, line 46, strike out the word 'of" after "series"; and that the said Letters Patent should be read i Pag the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of April, "A. D. 1937.

(Seal) Leslie- Frazer alter-' nating current power of substantially constant.

inted specification with this correction therein that Acting Commissioner of Patents. 

